Facebook has begun testing a new system of charging fees for sending private messages to people who are not among a user's friends, adding a new revenue source while potentially opening the doors to contacting celebrities on the social network.

Facebook has begun testing a new system of charging fees for sending private messages to people who are not among a user's friends, adding a new revenue source while potentially opening the doors to contacting celebrities on the social network.

In December it introduced a $1 charge as part of a test to see if people were willing to pay to have messages delivered directly to a user's inbox, as if they were friends on Facebook. If they did not pay they could still send a message, but it would go to a special folder that generally receives substantially less attention.

Now, however, users will have no choice, as the free option is being axed and users will have to pay between $1 and $15, or up to £10 in the UK, to send just one message to someone outside their network. The larger fees will likely be restricted to celebrities, as a way to discourage spam, but also as a guaranteed income for Facebook, given the likelihood that many will want to contact the big names directly.

“We are testing a number of price points in the UK and other countries to establish the optimal fee that signals importance,” Facebook said in a statement. “Part of that test involves charging higher amounts for public figures, based on the number of followers they have.”

The social network is labelling the move as a good way to prevent spam, but the company has been looking for ways to monetise the network for a long time now, including the addition of promoted posts and other forms of advertising. There will be few who see this as anything other than a revenue gathering exercise, and the test will lead many to question the “free (and always will be)” slogan on the Facebook homepage.